A safety and arming device is a required element of a munition to ensure that the munition is not armed and detonated until the desired time. The safety and arming device (S & A) is part of a munition's fuze and prevents arming of the fuze until certain conditions are met.
It is desirable to provide a munition with at least two unique environments, conditions or occurrences to take place in order for fuze arming to occur. In many munitions, typically the first environment utilized is usually setback for gun fired munition fuzing. Setback acceleration of gun fired munitions, due to its large magnitude, is an easily mechanically sensed environment. Fuze power is frequently not available at setback, necessitating a mechanical environment sensor.
Effective mechanically sensed second environments may be more difficult to sense. For example, in some munitions the spin or number of rotations of the munition in flight can be used as a fuzing environment. However, environments such as the number of rotations can be difficult to mechanically sense, and not sufficiently unique.
In barrel fired munitions, a rifled or twist bore has grooves which impart the munition projectile with a high degree of spin. The spin provides improved accuracy and stability. The high degree of spin is often used as a second environment in twist bore barrel applications. In smooth bore weapons however, a high degree of spin is not imparted to the projectile. Thus, munitions of smooth bore weapons have not previously employed spin, or rotation count as a second environment.
As indicated, both setback and high levels of spin are relatively simplistic to sense mechanically and have been used to implement first and second environments for fuzing of artillery rounds employed in twist bore applications.
In the case of smooth bore applications, such as smooth bore mortars, high G levels at firing may be employed as a first environment, but because no spin is imparted to the mortar, use of spin as a second environment is problematic. In past applications, mortar rounds have typically included wind driven turbines to release locks or generate power to provide a second fuzing environment. This has created a significant logistic problem, as entirely different fuze families have resulted, for example, twist barrel artillery round fuzes and smooth bore mortar fuzes.
While spin is not imparted to smooth bore projectiles via barrel twist, some level of spin is necessary to reduce dispersion, and thus increase accuracy, of the fuzed projectile. This spin is generally imparted to the round via canted fins inducing spin due to air flow after entry of the projectile into the air stream. The spin is generally about two to three times the aerodynamic resonance of the projectile, and is typically in the tens of hertz as opposed to the spin imparted to twist bore projectiles which is often in the thousands of hertz. In the past, measuring and utilizing the low spin rates of smooth bore projectiles as a second fuzing environment has not been practical.
It is a goal of at least one embodiment of the present invention to provide an electronic spin sensor capable of detecting the fin induced lower spin necessary to reduce dispersion in all smooth bore rounds. The fin induced lower spin may be detected within a time window to produce a unique second environment detectable by the sensor.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.